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Sakib816 , 01-26-2024, 03:23 PM

What is the function of POK1 and POK2 pin in this SMPS controller? And why have they been pulled up? At how many volts are needed to pulled up these 2 pins ? What will be the problem if pulled down? And how much actual input voltage should be given to these 2 enable pins > En1 and En2< in this SMPS controller?

QDrives , 01-26-2024, 04:21 PM

Q: "What is the function of POK1 and POK2 pin in this SMPS controller?"
A: It states it clearly in the datasheet: https://www.renesas.com/us/en/document/dst/isl6236-datasheet
"SMPS1 Power-Good Open-Drain Output. POK1 is low when the SMPS1 output voltage is more than 10% below the normal regulation point or during soft-start. POK1 is high impedance when the output is in regulation and the soft-start circuit has terminated. POK1 is low in shutdown."

Q: And why have they been pulled up?
A: They are pull-up because they are used.

Q At how many volts are needed to pulled up these 2 pins ?
A "VCC, EN, SKIP, TON, PVCC, POK to GND . . . . . . . . .-0.3V to +6V"

Q: What will be the problem if pulled down?
A: That you cannot use them. They are not needed for the controller itself.

Q: And how much actual input voltage should be given to these 2 enable pins > En1 and En2< in this SMPS controller?
A: "EN1, EN2 Input Voltage
Clear fault level/SMPS off level max 0.8 V
Delay start level 1.7 ... 2.3 V
SMPS on level min 2.4 V"

Mini , 01-26-2024, 05:01 PM

To add @QDrives answer about second question why pull-ups are used. I think the OP doesn't understund what open drain means. If he did, he would understund why pull-ups are needed and what pull-down would do. I recommend OP to just google "open-drain output". It is very common in electronics. I will give you a random video link to watch which should explain it quite well: https://www.youtube.com/watch?app=desktop&v=XaKdl0e9STU

Robert Feranec , 01-27-2024, 07:47 AM

and I would like to add, it is intentionally open drain and using a pull up, because often regulators are connected to circuits with different voltages and this way, the pull up can be connected to the same voltage as the chip/circuit where the POK is connected without using any additional buffers or level translators + this way also multiple POK signals from multiple regulators can be connected together and it will only go up if all regulators are working correctly - again it helps to simplify the circuit

Sakib816 , 02-24-2024, 12:37 PM

Does the VCC pin in the SMPS (ISL6236AIRZ) function as an input power supply pin or an output power supply pin? What is the voltage limit for VCC? How about the PVCC pin?

QDrives , 02-24-2024, 12:55 PM

On page 7 of the datasheet it states:
"3 VCC Analog Supply Voltage Input for PWM Core. Bypass to GND with a 1µF ceramic capacitor."
"19 PVCC PVCC is the supply voltage for the low-side MOSFET driver LGATE. Connect a 5V power source to the PVCC pin and
bypass with a 1µF MLCC ceramic capacitor. Refer to Figure 69 - A switch connects PVCC to VCC with 10when in
normal operation and is disconnected when in shutdown mode. An external 10 resistor from PVCC to VCC is
prohibited as it will create a leakage path from VIN to GND in shutdown mode."

The absolute maximum rating states that VCC and PVCC need to be within -0.3...+6V

Page 23 has an application example.

Perhaps it is wise to learn how to read a datasheet: https://www.youtube.com/watch?v=1EXXqWweTkI

Sakib816 , 02-24-2024, 02:09 PM

The VCC pin provides a +5V supply voltage, so it is an output pin. Isn't that correct? On the other hand, PVCC is connected to a +5V source, so it is an input pin.🙂

Robert Feranec , 02-24-2024, 03:47 PM

When I was working with the chip, I remember having the same question. I think I figured that out based on the block diagram on page 25, reference circuits on the pages before (22-27) and some measurements. Looks like the 5V LDO can power up PVCC (so this looks like an input) and PVCC can then connect to VCC (internally or externally). So both looks like an input (confirms what the description says), the output is from the LDO https://www.renesas.com/us/en/document/dst/isl6236a-datasheet

Sakib816 , 02-25-2024, 03:52 AM

Thanks @Robert Feranec . I considered VCC as the 5V output from a reference design which you had designed a while ago 🙂.

QDrives , 02-25-2024, 07:53 PM

In all application circuits VCC is only shown as a connection to a decoupling capacitor. Yet the datasheet mentions "Analog Supply Voltage Input for PWM Core".
I would not consider this as an output other than the connection of the capacitor.

Sakib816 , 02-27-2024, 09:52 AM

This reference design indicates that the VCC pin of the SMPS controller is linked to the EN_LDO pin, activating the LDO function. If the VCC pin is treated as an input, it raises the question of why it is connected to the EN_LDO pin. As per the datasheet, the EN_LDO pin must be set to logic high for the LDO function to be enabled.

Robert Feranec , 02-27-2024, 12:10 PM

My initial circuit was based on the reference board (which we had) - and they used this magic connection. I remember when I was creating the initial circuit, I had exactly the same questions 🙂 but I really don't remember where I found the information which answered them.

Sakib816 , 02-27-2024, 12:33 PM

Thank you @Robert Feranec. So, is the connection shown in this reference design wrong?🙂🙂

Robert Feranec , 02-27-2024, 12:42 PM

the connection is correct, it is just hard to find where it is explained how it works

Robert Feranec , 02-27-2024, 12:45 PM

https://www.renesas.com/us/en/document/mat/isl6236eval2-user-guide

Robert Feranec , 02-27-2024, 12:46 PM

Sakib816 , 02-27-2024, 03:18 PM

Thank you @Robert Feranec for helping . It’s very confusing task to find this 🙂.

QDrives , 02-27-2024, 09:31 PM

Did you try to contact Renesas or a distributor about this?

Sakib816 , 02-28-2024, 08:04 AM

Unfortunately, No. I just want to learn and try.

QDrives , 02-28-2024, 08:30 PM

Well, you have learned that datasheets can be terrible.

Sakib816 , 02-29-2024, 02:27 PM

Hi @Robert Feranec,
I have some questions. How do I properly select the output indicator and capacitor for this SMPS controller based on its required output current, switching frequency, output and input voltage? The input voltage range is 5V to 24V. What is the recommended output ripple current in percentage? Besides, in this SMPS controller (ISL6236AIRZ), from the datasheet, the output current is 100 mA. So how does the output current become 5A in the reference design? Dual-channel N-MOSFETs are used on the output side of this SMPS controller. It would be beneficial if you could provide me with the right guidelines. I have seen the datasheet and found the equation for indicator selection, but I am confused about the inductor and capacitor value selection process.

Mini , 02-29-2024, 03:45 PM

Im not familiar with this chip and not even read through datasheet, but i made quick look and seems you are already mixing different power supplies. Looking at the block diagram on page 25 this chip has 2 SMPS and LDO. 100 mA is and LDO current not SMPS current. They are totally different. That 5A max comes from VIN. Also when choosing inductor and capacitors you have several examples on pages 21-24. If you don't know how to calculate it, use some reference values. You can tweak that later on real board if needed.

Robert Feranec , 03-01-2024, 06:09 AM

I agree with @Mini